1. Field of the Invention
This invention relates to a packet transmission system for a local area network, and more particularly to a packet transmission system therein a telephone line or a twisted-pair cable which is economical and easy to handle is employed as a transmission medium.
2. Description of the Related Art
The local area network (LAN) has achieved a rapid development, and in recent years, much attention has been and is paid to a local area network which employs a telephone line or a twisted-pair cable which is easy to handle and inexpensive.
Several packet transmission systems are conventionally available. Representative ones of conventional packet transformation systems are the IEEE Std. 802.3 Type 10BASE-T (StarLAN 10, Twisted-Pair Ethernet) and the IEEE Std. 802.9 IVDLAN (Integrated Video, Voice and Data LAN) of the 802 Committee Standards of the Institute of Electrical and Electronic Engineering, Inc. (IEEE). According to the former system, the transmission rate is 10 Mbit/sec and the transmission range is about 100 m, and according to the latter system, the transmission rate is 4 Mbit/sec and the transmission range is about 450 m or so.
With such conventional packet transmission systems, however, since generally the transmission distance decreases as the transmission rate increases, in order to build up a LAN wherein, for example, the transmission rate is 16 Mbit/s and the transmission range is 400 m, an expensive coaxial cable must be employed. Accordingly, there is a problem that the cost for construction and maintenance of the system is high.